Photoproduction experiment with polarized HD target

Report
Development of the
polarized Hydrogen-Deuteride (HD) target for
double-polarization Experiments at LEPS.
EMIN-2012
RCNP Osaka University.
Osaka, Japan
Takeshi Ohta
Introduction
Background
The hadron photoproduction of the ϕ, K, η, and π0 mesons is studied by using linearly
polarized photon beams with energies of E γ = 1.5 ∼ 2.9 GeV at SPring-8 (LEPS).
These hadron photoproduction experiments have been carried out with unpolarized
target.偏極標的があれば、、、
We plan to carry out hadron photoproduction experiments by using polarized photon
beams and the polarized target.
Objective
Development of the polarized Hydrogen-Deuteride (HD) target for doublepolarization Experiments at LEPS.
We plan an experiment with polarized HD targets to
investigate the ss content in the nucleon by measuring
double polarization asymmetries
in the gp -> fp (gn -> fn ) reaction
EMC (European Muon Collaboration) reported that the contribution of
the spin of the quark to that of the proton is very few.
SMC (Spin Muon Collabollation) () reported that strangeness quark may
be contained 10−20% in the nucleon.
HAPPEX Collaboration reported the limitation to the strangeness form factors,
and these is nearly zero.
Presence of the strange quark content in the nucleon is
not conclusive. New data using different reactions play an
important role.
γp→fp reaction
In the reaction of γp→fp , there are four main reactions as follows
Cross Section at Eg = 2.0 GeV
Strangeness quark content is assumed to be
Pomeron exchange 0%
Pomeron exchange
uud knockout
One pion exchange
ss knockout
One pion exchange
ss knockout
uud knockout
It is difficult to evaluate a cross section from ssbar knockout. Pomeron exchange is dominant
A.I.Titov et al. Phys. Rev. C58 (1998) 2429
Measurement value CBT (Beam Target asymmetry)
Double polarization asymmetry.
g (I=1)
Nucleon (I=1/2)
Beam-Target double spin asymmetry
at Eg = 2.0 GeV
Strangeness quark content is
assumed to be 0% (Solid), 0.25%
(Dashed), and 1% (Dot-dashed).
A.I.Titov et al. Phys. Rev. C58
(1998) 2429
Beam target asymmetry CBT is very sensitive to the ss-bar content in the nucleon
Black circle is obtained at SPring8 at 2004
[T. Mibe, W. C. Chang, T. Nakano et al.
Phys. Rev. Lett. 95 182001]
Bump structure was found in K+L(1520)
gp -> K+L(1520)
H. Kohri et al. Phys. Rev. Lett. 104 (2010) 172001
Differential cross sections
Need the polarized nucleon target in advanced studies !!
We have to understand this bump structures to evaluate the CBT exactly.
LEPS Facility
a) SPring-8
SR ring
Collision
8 GeV electron
Recoil electron
Polarization degree of g-ray is
98%(Linearly) and 100%(circualry).
Beam energy is 2.4 ~ 3.0 GeV b) laser hutch
Intensity is ~106 g/s
Electron tagging
Laser light
c) experimental hutch
Top view of experimental hutch.
(set up the experimental refrigerator for HD target)
HD is heteronuclear diatomic molecule consisted by hydrogen and deuteron
Polarized method
We use the statistical method by cooling down and keeping the HD target at 10
mK with 17 Tesla for a few months (Brute-force method).
Advantage and disadvantage
Advantage: Dilution factor is good. (the number of H’s / the number of nucleons)
HD = 1/3, NH3 = 3/17, C4H10O = 10/74
Disadvantage: The HD target needs thin aluminum wires (at most 20% in weight)
to improve the cooling power to solid HD.
Size of Target
Diameter is 25 mm. Length is 50 mm.
Relaxation time
Under the condition of the experiment
(T=300 mK and B=1 Tesla) ,
the relaxation time is possible to be longer
than several months .
Polarization of H and D
T : high
N-
| -1/2>
E=mpB
|+1/2>
N+
 PH 
 PD 
v
17 T
1T
N - NN  N-
 tanh(
)
kT
N - NN  N0  N-
10 mK
14 mK
4.2K
E
4 tanh(

E
)
2 kT
E
2
3  tanh (
)
2 kT
Hydrogen
94.0%
84.5%
0.024%
Deuteron
31.9%
23.6%
0.0050%
T : low
Frozen polarization mechanism
The polarization of HD is produced by
the spin-flip with small concentration
of ortho-H2 (~0.01%) included in HD
at 17 Tesla & T=14 mK
Most of ortho-H2 has converted to
para-H2. Polarization degree of HD
is kept for about one year at 1 Tesla
& T=300 mK
ortho
para
para
B
B
Concentration of o-H2
Decrease with time.
Time constant is 6.5 days
Relaxation time
Increase with time. The length of relaxation time
depends on the concentration of o-H2
Polarization
The Polarization grows with time. Growing rate
depends on relaxation time.
When the relaxation time is very short, the
polarization reaches Thermal Equilibrium
Initial concentration of o-H2 is important for the polarization degree and
relaxation time of HD target.
Measurement of NMR spectra
NMR signals obtained at
4.2 K as a calibration point
after pouring HD gas
(Polarization = 0.024%)
Meas. Environment
• Temperature:4.2 K
• Magnetic field:1 Tesla
Single coil
HD target was putted in
DR for 53 days with 14 mK
and 17 Tesla
Meas. environment
• Temperature:300 mK
• Magnetic field:1 Tesla
Polarization : 40.8±2.3%
Relaxation : 112.8±0.1 days
Results 1st prodection



17 Tesla &14 mK
polarization
Relaxation time
Expected
84.5%
3 month ?
measured
41.4% +/-3.1%
106+/-16 days
The temperature of the HD cell might be higher than 14 mK.
The heat transfer is not so good between different material
because of the presence of Kapitza resistance at boundries.
The linearity between NMR signal height and polarization
Since the magnitude of the signal changes 1000 times, we discuss
whether NMR system is linear or not in dynamic range
Concentrations of ortho-H2 might be too small
In this case the relaxation time of H in HD was to be very long at
start time. Polarization did not grow.
Requirement of portable NMR system
1.2 K
1T
14 mK
17 T
300mK
1T
NMR measurements are required at various points denoted by ○.
Portable NMR measurement system has been developed for handy transportation.
NMRシステムの概要図
Conventional
ダイヤグラム図
使用している機器
・信号発生器
・ロックインアンプ
・オシロスコープ
・ネットワークアナライザ
・フィルタ
・マルチメーター
Portable NMR system
使用したモジュール
・PXI-1036(シャーシ)
・PXI-8360(コントローラ)
・PXI-5404(信号発生器)
・PXI-5142(ADC)
ダイヤグラム図
Portable NMR system (PXI-NMR)
ロックインアンプ





重さ、空間スペース、
コスト全てにおいてダウン
手順が簡素化
自動調整&自動測定が可能。
測定システムのカスタマイズが可能
他人にわかりやすく説明できる
80 Kg
7.1 Kg
オシロ&スペアナ
ネットワークアナライザ
W 600
D 600
H 2000
W 250
D 200
H 200
600万
150万
Comparison of S/N ratio
S/N比は従来のNMR測定システムに比べて約半分。
偏極測定での使用は十分と考える
各NMR測定で条件を揃えて測定が可能に!
Quadrupole mass separator was used for analysis of components in the HD gas.
HD gas are mass-separated according to the
mass/charge ratio (u/e).
But this system have a problem.
Fragmentation problem
When HD gas is ionized, H+ and D+ ions is produced by electron bombarded.
Fragmentation factor
D+/HD = 0.4%
H2+/HD ~0.001% <= We want to measure!!
New analyzer is required avoiding the problem for analysis of HD gas precisely
New gas analyzer
GC-QMS (Gas Chromatograph and Quadrupole Mass Spectrometer)
distiller
Components in the HD gas are separated by using the difference of retention time in
the column and the mass/charge ratio measured by the QMS.
The column is cooled down to about 110 K. ////to attain a reasonably long retention
time for the hydrogen and deuterium gases.
軽い粒子は早く、思い粒子は遅い 通過時間の差でわける
p-H2 , o-H2 , HD, and D2 components is separated by elapsed time in the GC completely.
The measurement is possible with 0.001% precision for the components.
p-H2 and o-H2 is separated.
テーブルを作る
New analyzer for HD gas is developed and fragmentation problem is avoided
蒸留塔1号機と2号機
写真
外観図
充填物



Distiller is designed basis on chemical industries.
NTS is designed 37.9
Simulate from design of new distillator
H2
HD
D2
Commercial HD gas
Before distillation
After distillation
New distiller
Old distiller
Erapse time vs Concentration
Concentration [%]
1.0E+02
H2 top [%]
D2 top [%]
1.0E+01
1.0E+00
1.0E-01
1.0E-02
1.0E-03
11/21
11/25
11/29
Elapsed time
12/3
12/7
H2
HD
D2
Run 3
H2
HD
D2
Initial
75.00%
24.96%
0.03%
Initial
99.963%
0.035%
0.002%
Distilled
0.03%
97.71%
2.26%
Distilled
~0.001% ~99.999% ~0.001%
6 days (not need removing D2)
Term
20 days for removing H2
14 days for removing D2
Term
NTS
14
NTS
37.2 ± 0.6
(Designed 37.9)
 The new analysis system enabled us to observe p-H2 , o-H2 , HD, and D2
separately.
 Components in HD gas enable us to analyze with a high precision of 0.001%
 Distillation term is shorten from 34 days to less than 6 days
We can control the concentration of o-H2 and D2 when HD target is produced.
New HD distiller and new gas analyzer enable to us to optimize aging time.
(In my calculation, the aging time is able to shorten to ~2 weeks)
T. Ohta et al. NIM-A 640 (2011) 241
T. Ohta et al. NIM-A 664 (2012) 347
3rd production
HD gas for target was produced Distiller and analyzed.
Concentration of o-H2 in prepared HD gas for the target is 2x10-4%.
NMR signal obtained after pouring HD
gas at 500 mK.
Polarization calculated from Boltzmann
low is 0.2% at 500 mK
NMR signal obtained after 2 month of
aging time.
Polarization : 30%
Relaxation : 40~100 days
*Preliminary
Conclusion : 2x10-4% is too low for production of HD target.
HD single crystal
HD target includes the aluminum wires of 20% in weight.
HD single crystal a hexagonal single crystal and have a good thermal
conductivity of HD target.
The thermal conductivity of normal HD target is < 0.1 W/Km
kL : perpendicular
k|| : parallel
Pour the HD gas
K||
kL
In the future, we will replace the HD single crystal from
normal HD target included aluminum wires
Summary







We have been developing for the complete double polarization
experiment to investigate strangeness quark contents of the
nucleon.
We tried the 1st production of the HD target in 2009.
The polarization was 41.4% and relaxation time was 106 days.
We can measure the NMR signal anywhere.
We can control the concentration of o-H2 and D2 in the HD gas by
new gas analyzer and new distiller.
We tried the 2nd production of the HD target in 2012.
The polarization was 30% and relaxation time was 100 days.
Transporting the polarized HD target from RCNP to SPring-8
Starting f-meson experiment using the polarized HD target.
Backup
New data for strangeness in the nucleon
Recently, HAPPEX
Collaboration reported
new data!!
Acha et al.
Phys. Rev. Lett.
98 032301 (2007)
[18] N.W. Park and H. Weigel, Nucl.
Phys. A541, 453(1992).
[19] H.W. Hammer, U.G. Meissner,
and D. Drechsel, Phys.Lett. B 367,
323 (1996).
[20] H.W. Hammer and M. J. RamseyMusolf, Phys. Rev. C 60, 045204
(1999).
[21] A. Silva et al., Phys. Rev. D 65,
014016 (2001).
[22] R. Lewis et al., Phys. Rev. D 67,
013003 (2003).
[23] D. B. Leinweber et al., Phys. Rev.
Lett. 94, 212001 (2005);97, 022001
(2006).
Presence of the strange quark content in the nucleon is
not conclusive. New data using different reactions play an
important role.
We plan to measure the double polarization
asymmetry for the gp -> fp (gn -> fn ) reaction
16 observables for the gp
Observable
Many groups
LEPS
CLAS and SAPHIR
measured
for K+L and K+S0
Recently
CLAS measured
for K+L and K+S0
KY reaction
Polarization
Beam
Target
Single polarization & Cross section
ds/dW
S
T
P
linear
-
Hyperon
transverse
-
y
Beam-Target double polarization
G
H
E
F
linear
linear
circular
circular
z
x
z
x
-
-
Beam and Recoil hyperon double polarization
Ox
Oz
Cx
Cz
linear
linear
circular
circular
-
-
x
z
x
z
フォトン偏極は直線と円 Target and Recoil hyperon double polarization
標的偏極は Longitudinal
Tx
x
x
と Transverse
Tz
x
z
Lx
Lz
-
z
z
x
z
gp->phi p cross sections
この角度とエネルギーを避けてデータ解析する
Pentaquark (q+ uudds ) search
Although the results are positive, statistics is not enough in both data.
We took data with 3 times higher statistics than Data (2) in 2006-2007.
Data analysis is underway now.
New data will appear soon.
T. Nakano et al. PRL 91 (2003) 012002
gC reaction
(2)
gd reaction
Counts
Counts
(1)
T. Nakano et al. PRC 79 (2009) 252
Mass (GeV/c2)
Mass (GeV/c2)
BNL-E949 spectrometer was transported to SPring-8
来年メイン検出器TPCがインストールされる
@SPring-8 LEPS2 experiment hutch
Collaborators of HD project
K. Fukuda, M. Fujiwara, T. Hotta, H. Kohri, T. Kunimatsu,
C. Morisaki, T. Ohta, K. Ueda, M. Uraki, M. Utsuro, M. Yosoi,
(RCNP, Osaka)
S. Bouchigny, J.P. Didelez, G. Rouille
(IN2P3, Orsay, France)
M. Tanaka
(Kobe Tokiwa University, Japan)
Su-Yin Wang
(Institute of Physics, Academia Sinica, Taiwan)
核子内のストレンジネスの探索
肯定的結果
偏極ミューオン,偏極陽子深部非弾性散乱 (EMC)
J. Ashman et al., Nuclear Physics B 328 (1989) 1.
・・核子のスピンを構成するものとしてssがu,dクォークに匹敵する
否定的結果
電子陽子弾性散乱 パリティの破れ (HAPPEX)
A. Acha et al., Phys. Rev. Lett. 98, (2007) 032301.
・・電子陽子弾性散乱ではストレンジネスのGE、GMは0に近い
偏極標的を使用した最初の実験として核子
からssを叩き出す実験を計画している
γp→φp反応
Future plan
After aging HD target, condition is
changed
The temperature and magnetic field are different on the production and experiment
Low magnetic field and high temperature may decay the polarization of HD.
Aging
B=17 Tesla
Temperature of polarized HD
Temperature must
be increased.
Magnetic field must
be decreased.
TC1
In truck
B=1 Tesla
TC1
Experiment
at SPring-8
B=1 Tesla
Temperature (K)
Magnetic Field (Tesla)
Magnetic field to polarized HD
Aging
T=14 mK
TC2
In truck
T=1.2 K
Experiment
at SPring-8
T=300 mK
TC2
Time (hour)
Time (hour)
偏極度とAging timeの関係 ~モデル式~
Fig. A
偏極度は温度が低いと
ころから高いところへ
上昇する場合、偏極が
その場合偏極度は緩和
時間 T1 に依存し次の式であら
減衰する。
わされる。
P  PTE exp( - t / T1 ・・・・・(1)
)
しかし偏極
HD 標的の場合、
長くなっていく。この
T1 は ortho - H2 が para - H2 に転換することによっ
場合 T1 は以下の式であらわせ
T conv は ortho - H2 から para - H2 に転換する時間である
この転換時間が非常に
ここで言いたいのは
T0
T1 

うこと。この式を
Fig.A にプロットする
・・・・・(2)
exp( - t / T conv )
(1) 式であるが、これは
微分方程式から式を組
dP
る。
T0
N ortho - H 2
ここで
る。 T 0は初期の緩和時間、
。
速いと T1 の増大も非常に速くな
T1 が時間に依存するとい
T1
て
T1 が時間に依存しない場
み立てる必要がある。
合の式であり時間に依
そこで単位時間内に偏
存している場合は
極する数を
dp / dt として
Aging time
 (1 - P ( t )) 
dt
dP
1 - P (t )
dP
1 - P (t )
dP
1 - P (t )
  dt  は T1 の逆数なので
 1 / T1 dt T1 に式(2)を代入して

exp( - t / T conv )
Fig. B
dt 両辺を積分
T0
- log( 1 - P ( t ))  -
T conv exp( - t / T conv )
C
P
T0
1 - P ( t )  exp( -
T conv
T0
結果偏極度の時間依存
exp( - t / T conv )  C )
の式は以下のようにな
る。
 T

P  1 - exp  - conv (exp( - t / T conv ) - 1) 
T0


転換時間 T conv  6.5日の場合
 6.5

P  1 - exp  (exp( - t / 6 . 5 ) - 1)  この式を
T
0


Fig.B にプロットする。
Aging time


問題点を羅列
First productionをやったけれども
Simulate!!
• Ortho-H2 is,,,,,,
• Too poor
normal
P  PTE exp( - t / T1 )
but ...
T1 
dP
T0

N ortho - H 2
T0
Z (T ) exp( - t / T conv )
 (1 - P ( t )) 
dt
dP
1 - P (t )
dP
1 - P (t )
dP
1 - P (t )
  dt
 1 / T1 dt

Z (T ) exp( - t / T conv )
log( 1 - P ( t ))  1 - P ( t )  exp( -
dt
T0
1
Z (T ) exp( - t / T conv )
T conv
T0
1
Z (T ) exp( - t / T conv )
T conv
T0
C
 C)
too many
FAFP (Transfer polarization from
H to D) Second transition
First transition
mD=-1
Init
mH=-1/2
mD=0 mD=+1
mD=-1
mH=-1/2
PD=0
mD=0 mD=+1
PD=0.33
mH=+1/2
mD=-1
mH=-1/2
mH=+1/2
mD=0 mD=+1
mD=-1
mH=-1/2
mD=0 mD=+1
RF in
mH=+1/2
mD=-1
mH=-1/2
Nature
decay
mH=+1/2
mD=0 mD=+1
mD=-1
mH=-1/2
PD=0.33
mH=+1/2
mD=0 mD=+1
PD=0.58
mH=+1/2
Saturated forbidden transition
(SFT)
• This method uses frequency modulated RF to produce a rapid
succession of low efficiency spin transfers by passing through
the resonance many times.
• The D polarization can reach 31.1%.
M. Bade
PHD thesis
2006
Initial polarization
is assumed
to be 100%
as a result……
In Beam Cryostat (IBC)
[email protected]
H : T1= 106±16 days
Storage Cryostat (SC)
[email protected]
H : T1= 11.6±1.5 days
Transfer Cryostat
(TC1,TC2)
[email protected]
H : T1= 7.5±0.7 days
Chapter 4 |偏極度と緩和時間の考察
RCNP (2009)
LEGS (2007)
偏極度
40.8± 2.3 %
~60%
緩和時間
112.8±0.1 days
≧1 year
Aiging time
53 days
3 month
緩和時間について
アメリカのLEGSグループとの比較。緩和時間はLEGSが達成していた≧1
yearよりも短かった。エイジング期間はLEGSよりも短い53日
偏極度について・・・
偏極度を精度よく求めるためには4.2 KでのNMR強度の精度が重要
NMRのベースラインが不安定であったり、水素のバックグラウンドを含んでいるた
めにNMRの強度を精度よく評価出来ない
偏極度が期待されたもの(84%)より低かったことについて
• NMR測定本質における線形性が崩れている可能性
• o-H2の量が最適ではなかった
希釈冷凍機投入前にHDガスは蒸留器内で34日間蒸留されていた。その間oH2 がほとんどp-H2に転換していた可能性がある 。
o-H2を測定できる技術はなかった。
水素バックグラウンドの除去
NMRを測定したときに検出されるHD以外からの水素のNMR共鳴は偏極度
PXI-NMR|
を決定する際に不確かさの原因となる。水素のバックグラウンドの起因を突
き止め除去した。
HD有り。1.14mol入れた時
HD無し。Hの量は0.06mol以下
ベースラインのドリフトを改善
NMR測定時にベースラインがドリフトし、解析に影響した。
PXI-NMR|
ベースラインが安定するよう回路の温調(40℃)を試みた
(a) 温調なし
(b) 温調箱を閉め恒温状態
(c) 温調箱を閉めて温調する
S/N比は約10倍に向上した。
まとめ
温調によりS/N比を10倍にした
PXI-NMR|
•
• エナメル線のコイルをテフロン銀線に交換することによ
り水素の強烈なバックグラウンドを取り除いた
• ポータブルNMR測定システムで至る所でNMR測定が
可能になり、また測定条件を揃えることが可能になった
2011年2月にパブリッシュ
T. Ohta et al. NIM-A 633 (2011) 46
• EMIN-2012は物理の話をするところ
• 時間30分(トーク20分 質疑10分)
• タイトル
Development of the Polarized Hydrogen-Deuteride
(HD) Target for Double- Polarization Experiments at
LEPS.
物理と開発系の話のバランスが難しい。
BACKUP
蒸留塔第1号機
市販HDガス(H2 3% :D2 3%)を投入
STEDMAN
PACKING
H2
HD
D2
蒸留直後
75.00%
24.96%
0.03%
蒸留後
0.03%
97.71%
2.26%
HD
Erapse time vs Concentration
1.0E+02
Extraction
Extraction
H2
HD
HD
Concentration1[%]
1.0E+01
H2 top [%]
D2 top [%]
1.0E+00
1.0E-01
1.0E-02
D2
D2
1.0E-03
11/19 11/21 11/23 11/25 11/27 11/29 12/1 12/3 12/5 12/7
TIME
温度及びn-H2の濃度緩和時間の関係
Walter N. Hardy Phys. Rev. Lett. 17 (1966) 1258
4.2Kでのo-H2及びp-D2とH及びDの緩和時間
LEPS experiment in the past.
(A) f meson photoproduction
f meson production on Li, C, Al, Cu
*gp -> fp
gd -> fd
gn -> fn
gp -> fp, gn -> fn
T. Ishikawa et al. Phys. Lett. B 608 (2005) 215
T. Mibe et al. Phys. Rev. Lett. 95 (2005) 182001
W.C. Chang et al. Phys. Lett. B 658 (2008) 209
W.C. Chang et al. Phys. Lett. B 684 (2010) 6
W.C. Chang et al. Phys Rev. C 82 (2010) 015205
(B) Strangeness photoproduction
gp -> K+L, gp -> K+S0
gp -> K+L, gp -> K+S0
gn -> K+Sgp -> K+L
gp -> K+S-(1385)
gp -> K+L(1405), S0(1385)
gp -> K+L(1520)
*gp -> K+L(1520)
R.G.T. Zegers et al. Phys. Rev. Lett. 91 (2003) 092001
M. Sumihama et al. Phys. Rev. C 73 (2006) 035214
H. Kohri et al. Phys. Rev. Lett. 97 (2006) 082003
K. Hicks et al. Phys. Rev. C 76 (2007) 042201(R)
K. Hicks et al. Phys. Rev. Lett. 102 (2009) 012501
M. Niiyama et al. Phys. Rev. C 78 (2008) 035202
N. Muramatsu et al. Phys. Rev. Lett. 103 (2009) 012001
H. Kohri et al. Phys. Rev. Lett. 104 (2010) 172001
(C) Pseudoscaler meson photoproduction
gp -> p0p
gp -> hp
M. Sumihama et al. Phys. Lett B 657 (2007) 32
M. Sumihama et al. Phys. Rev. C 80 (2009) 052201(R)
(D) Search for exotic resonance state
Pentaquark search
Pentaquark search
T. Nakano et al. Phys. Rev. Lett. 91 (2003) 012002
T. Nakano et al. Phys. Rev. C 79 (2009) 025210

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